1. Field of the Invention
The present invention relates to electrical testing devices in general, and more particularly to a testing kit for testing the operation of various components of street lights and similar lighting fixtures employing electric arc discharge lamps as their light sources.
2. Description of the Related Art
There are already known various devices for testing electrical equipment, among them such which are especially suited or specifically designed for testing street lamps and similar high-intensity lighting devices, such as those employing electric discharge lamps, especially high pressure sodium lamps, as their sources of light. Light fixtures of this kind are known to those versed in the area lighting field as luminaires and will be referred to herein by that name.
Before discussing the state of the art, it is to be mentioned, without going into unnecessary detail, that in many street lighting systems each street lamp is equipped with its own photoelectric device that is strategically located so that its photoelectric sensor intercepts ambient light but not that issued by the luminaire of that street lamp, and its control circuitry is interposed in the wiring of the individual street lamp between the electric network that supplies electric power to a usually considerable number of street lamps distributed along a street, highway or similar route, and the electric circuit that is associated with the individual luminaire. Such electric circuit ordinarily incorporates, besides a socket that is provided with an internal, so-called mogul, thread into which an externally threaded portion of the light source or lamp proper is threaded, a starter and a ballast. The constructions and functions of the latter two devices are so well known that it would be an exercise in futility if it were attempted to describe them here in detail. Suffice it to say that the starter is operative for generating a high-voltage starting pulse that establishes the arc discharge within the lamp, while the ballast helps to sustain such discharge once established.
Whenever there is sufficient ambient light, the photoelectric sensing device shuts the luminaire off, that is, it disconnects the electric circuit of the particular street lamp from the electric power supply network. However, there may be a plethora of other or additional reasons why the lamp does not issue light when called for, of which failure of the lamp itself is just one. Yet, because the photoelectric device is supposed to prevent the affected street lamp from operating during daytime, the failure of a particular street lamp is not detected or reported until it gets dark outside. At that time, it is usually too late to send a repair crew over to fix the light. As a matter of fact, for safety and other reasons, street light repairs are typically conducted when it is light outside.
Of course, it may be either the photoelectric sensing device itself or the wiring leading to or from a socket that receives the photoelectric sensing device that is faulty. To test this, there has been developed a testing instrument having electrical contacts substantially corresponding to those of the photoelectric sensing device to enable interposition of the testing device instead of the photoelectric sensing device between the incoming wiring and that leading to the aforementioned electric circuit of the luminaire. The testing device includes a light-emitting diode that lights up when the presence of supply voltage is detected. By the same token, it indicates by not lighting up that the incoming wiring to, or the socket for, the photoelectric sensing device is defective. Moreover, the testing device, like the photoelectric device if fully operational, permits the supply voltage to pass therethrough to the luminaire. If the lamp of the latter strikes and begins to glow, a conclusion may reasonably be dram that it was the photoelectric sensing device that was at fault. However, to make sure, it is customary to reinstall the original photoelectric sensing device and use the so-called "glove test" (consisting of the technician placing his or her glove over the light-admitting orifice of the photoelectric sensing device to shield it from ambient light) to determine if the luminaire lamp lights up after the replacement of the photoelectric sensing device. If it does, then the problem was probably caused by insufficient or lacking electrical contact in the photoelectric sensing device socket and has likely been solved by the removal and reinstallation of the photoelectric sensing device. No further action is necessary. If it does not, then the next step is to replace the photoelectric sensing device by another one and use the glove test to see if the situation has been remedied by such substitution. If it has not, or if the luminaire lamp did not light up when the testing device was substituted for the photoelectric sensing device but the light-emitting diode of the testing device was on, then the fault is either with the luminaire lamp or its circuitry, or with the outgoing side of the photoelectric sensing device socket, of with the wiring connecting the socket with such circuitry.
Experience with this kind of testing device has shown that it is able to pinpoint or at least eliminate some of the reasons why the luminaire lamp does not light up. However, it was also established that it leaves much to be desired in certain respects. So, for instance, if the source of the problem is a short circuit in the wiring or circuitry downstream of the photoelectric device, then a substantial amount of electric current may flow through the testing device in a short period of time, thus damaging the same.
Moreover, even if the light of the testing device lights up during the testing, there is no assurance that the supply voltage detected is at a level sufficient for faultless operation of the luminaire lamp and its associated devices and circuitry, and there is no way to measure this voltage level while the testing by the testing device is in progress.
Last but not least, it is frequently difficult for the technician to determine whether or not the testing device light is lit, be it because, at the angle at which the technician is looking at the testing device, the light is obscured by other parts of the testing device or because, especially on bright sunny days, its light is difficult to discern over foreground or background reflections of the sunlight. Inasmuch as the angle of observation is given by the way the photoelectric device socket is mounted on the street lamp and the way the technician is situated, often already on a rather precarious perch, with respect to the street lamp, reliable "reading" of the testing device light cannot always be assured, especially when the extent to which the technician may move without imperiling himself or herself is limited.
Once it has been established in the manner described above that the problem lies elsewhere than with the photoelectric sensing device or the wiring leading to it, the inquiry is continued but at a slightly different location and using a different testing instrument. More particularly, while an electrical flow path is established through the photoelectric sensing device socket such as by installing the previously discussed testing device therein, the luminaire lamp is removed from its socket and a base of the testing instrument is threaded in its stead into such socket. One known testing instrument of this type is equipped with two lights and with circuitry that causes one of the lights to light up and blink when the presence of a starting pulse is detected, while causing the other light to light steadily when the ballast is operating properly and the voltage detected in the luminaire lamp socket is sufficient for the luminaire lamp to operate. Thus, if both lights are on, it must be the luminaire lamp that is defective; if the first light fails to operate, then the fault is with the starter, and it is with the ballast when the second light is not on. If neither one of the lights of the testing instrument lights up, then it is probably the wiring between the photoelectric sensing device and the luminaire lamp circuitry, or such circuitry itself, that is defective, since it is highly unlikely that both the starter and the ballast would give out at the very same time.
Here again, however, the known testing instrument has certain drawbacks that make its use less than completely satisfactory. For one, the instrument is incapable of indicating anything more with respect to the incoming voltage than whether or not it is above a predetermined level, even though it is often desirable to establish at least the range in which this incoming voltage can be found.
Moreover, the known testing instrument is dedicated to testing the electric circuits and wires for a single type of luminaire lamp only, even though there are at least two types operating on the same network voltage (105 V) differing from one another in wattage (below or above about 150 W, respectively) and arc voltage (50/55 V vs. 100/130 V). Inasmuch as the technician frequently does not know beforehand which type of luminaire lamp and associated electric circuit he or she will encounter when reaching the location of the luminaire, he or she must come equipped with two such instruments, one for each of the luminaire lamp types, and determine which one is the proper one only after reaching such lofty location. This not only is rather inconvenient and cumbersome, but may result in incorrect diagnosis or even lead to damage to the testing instrument used if the latter is of the wrong type.
Additionally, the provision of the base of the testing instrument with a mogul thread compatible with that of the luminaire lamp socket makes the instrument difficult to install and use not only in terms of the time that it takes to screw it in and out of the socket, but also, and possibly more importantly, in requiring the technician to manipulate the instrument extensively while at an inconvenient location and possibly holding the removed luminaire lamp at the same time.